The present invention relates generally to implantable leads and catheters and more particularly to mechanisms for deflecting implantable leads and catheters to assist in guiding them through the vascular system.
Over the years, quite a number of mechanisms have been disclosed and employed to deflect catheters and implantable leads. These have taken the form of deflectable guidewires and deflectable stylets, typically operable from the proximal end of the lead or catheter, which controllably impart a curve to the distal portion of the lead or catheter. One group of devices comprise deflectable stylets or guidewires which employ a straight, tubular outer member with a curved inner member, the inner and outer members movable relative to one another. Examples of this type of deflection mechanism are disclosed in U.S. Pat. No. 4,136,703 issued to Wittkampf and U.S. Pat. No. 5,728,148 issued to Bostrom et al. Alternatively, deflection devices employing a curved outer member and a relatively straight inner member are also known to the art, as disclosed in U.S. Pat. No. 4,676,249 issued to Arenas and U.S. Pat. No. 5,040,543 issued to Badera et al. In devices of both types, the relative position of the inner member with respect to the outer member determines the degree to which the curved member (inner or outer) is allowed to display its preset curvature.
A more commonly employed approach to providing controllable deflection employs a generally straight outer member and a tension or push wire located within the outer member which on advancement or retraction causes the outer member to bend. Examples of such deflection mechanisms can be found in U.S. Pat. No. 4,815,478 issued to Buchbinder et al., and U.S. Pat. No. 4,940,062 issued to Hampton et al.
Particularly in the context of deflectable stylets intended for use in conjunction with implantable medical leads such as pacing and cardioversion leads, steerable stylets employing this third type of deflection mechanism are disclosed in U.S. Pat. No. 5,662,119 issued to Brennen et al., U.S. Pat. No. 5,170,787 issued to Lindegren, and U.S. Pat. No. 5,327,906 issued to Fideler et al, all of which are incorporated herein by reference in their entireties.
While all of the mechanisms disclosed in the above cited prior art patents are at least to some degree workable, there is still a perceived need for a deflectable stylet or guidewire which has the capability to impart a controllable, relatively small radius curvature to the distal end of a cardiac pacing lead or catheter and which is sufficiently durable to allow for repeated use.